In LTE Release 8/9/10, a physical downlink control channel (PDCCH) adopting techniques such as dynamic indication, implicit addressing, blind detection, full bandwidth diversity transmission and so on mainly for a scenario of homogeneous macro cellular networking has been proved to have excellent operating performance. In these systems, however, the PDCCH occupies one to three orthogonal frequency division multiplexing (OFDM) symbols (occupies two to four OFDM symbols in the case of a system bandwidth of 1.4 MHz), and downlink control information sent on each subframe is limited. However, with the introduction of a scenario of heterogeneous networking and the application of new techniques such as coordinated multipoint transmission (CoMP), inter-cell interference coordination (eICIC), carrier aggregation (CA) and so on in an LTE-advanced Release 11 (LTE-A R11) system, there has been an extremely increasing demand for control signaling, so the capacity of a downlink control channel becomes one of notable bottlenecks of system performance. Besides, the PDCCH performs diversity transmission with full bandwidth, thus causing a problem of failing to further obtain a beamforming gain, a frequency selective gain and the like brought about by transmission techniques such as downlink Multi-Input Multi-Output (MIMO) Beamforming and so on. Therefore, 3GPP RAN1 working group introduces an enhanced physical downlink control channel (EPDCCH) technique in standard customization for R11.
As shown in FIG. 1, the EPDCCH does not occupy resources of the PDCCH, but performs frequency division multiplexing with a physical downlink shared channel (PDSCH); that is, only the EPDCCH or the PDSCH is transmitted within one pair of physical resource blocks (PRBs) (resource blocks occupying 12 sub-carriers in frequency domain and occupying two time slots in time domain), thereby making it possible to obtain beamforming and diversity gains, increasing flexibility in interference cancellation on a control channel in heterogeneous networks and ensuring excellent coverage. The EPDCCH is one of important physical channels in LTE-A system, and it carries contents including some broadcast system information, paging instructions sent to some user equipment (UE), indication of resource positions of UE data channels, indication of modulation and encoding manners of UE data channel transmission, hybrid automatic repeat request (HARQ) information and uplink power control and the like. Therefore, whether or not signaling transmission on the EPDCCH is accurate directly determines the performance of the overall system. However, in the scenario of heterogeneous networking in the LET-A system, the introduction of small-power base stations such as Pico base stations, Femto base stations and so on causes the cell system capacity and the edge coverage to be improved greatly but causes the structure of inter-cell interference to become more complicated; and the existing interference coordination scheme on the control channel is too simple to satisfy requirements. Therefore, it is greatly desired to introduce a new interference coordination scheme on the control channel, so as to support accurate transmission of control channel signaling efficiently.
In addition, a reception speed of the EPDCCH of LTE-A serving as a core of system resource allocation and control information scheduling influences a response speed of the system greatly. A terminal detects control information on the EPDCCH by adopting blind detection, so it is necessary to adopt an effective mechanism to reduce the number of times of blind detection, making it possible to improve the response speed of the overall system. The EPDCCH comprises enhanced control channel elements (ECCEs), for carrying downlink control information (DCI), and the number of the ECCEs which constitute the DCI is called an ECCE aggregation level. Since there has been an extremely increasing demand for control signaling so that the capacity of the downlink control channel becomes one of notable bottlenecks of system performance, the EPDCCH is introduced, it is significant to reduce the ECCE aggregation level as much as possible, so as to save the space of the EPDCCH and thereby increase the network capacity.
According to the prior art, the ECCE aggregation level of the EPDCCH is controlled based on downlink quality information such as channel quality indication (CQI) and reference signal receiving power (RSRP) fed back by the user equipment, so as to ensure the reliability of the EPDCCH. For example, for the CQI scheme, a network layer may set mapping relationship between CQI values (0-15) and ECCE aggregation levels (1, 2, 4, 8, 6, 32), and a base station determines an aggregation level to be adopted based on the CQI fed back by the user equipment and the CQI-ECCE aggregation level mapping relationship; and for the RSRP scheme, an RSRP intensity threshold required by each ECCE aggregation level is necessarily determined, and an ECCE aggregation level for which an RSRP intensity threshold is less than the RSRP of the user equipment is selected to be used. However, upon adoption of for example coordinated multipoint transmission or other interference coordination schemes on the EPDCCH, actual receiving power of the user equipment and channel condition are very complicated, and thus both the schemes of determining the ECCE aggregation level are not applicable. In addition, a more flexible ECCE aggregation level adjustment scheme is also desired to satisfy different Quality-of-Service (QoS) requirements of the user.